U.S. patent number 4,028,132 [Application Number 05/635,017] was granted by the patent office on 1977-06-07 for cellulose solutions and products prepared therefrom.
This patent grant is currently assigned to International Playtex, Inc.. Invention is credited to Narayan Ganesh Kumar, Morton H. Litt.
United States Patent |
4,028,132 |
Litt , et al. |
June 7, 1977 |
Cellulose solutions and products prepared therefrom
Abstract
Solutions of cellulose in hydrazine are formed by dissolving
cellulose therein. The cellulose solutions formed may be utilized
for the preparation of fibers, films, foams or other cellulose
fabricated articles. Alternatively, the dissolution of cellulose in
hydrazine may be employed as a means for the direct extraction of
cellulose from lignocellulosic materials without the necessity of
pulping operations.
Inventors: |
Litt; Morton H. (University
Heights, OH), Kumar; Narayan Ganesh (Webster, NY) |
Assignee: |
International Playtex, Inc.
(New York, NY)
|
Family
ID: |
24546086 |
Appl.
No.: |
05/635,017 |
Filed: |
November 25, 1975 |
Current U.S.
Class: |
106/164.5;
536/56 |
Current CPC
Class: |
C08J
9/14 (20130101); C08B 1/003 (20130101); C08J
2301/02 (20130101) |
Current International
Class: |
C08B
1/00 (20060101); C08J 9/14 (20060101); C08J
9/00 (20060101); C08L 001/02 () |
Field of
Search: |
;106/163,122 ;260/212
;264/187,207 ;8/125 ;536/56 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
The Chemisty of Cellulose, E. Heuser, pp. 136, 137. .
Chem. Abst. 48:7893i, 1954. .
Chem. Abst. 66:77931z, 1967. .
Chem. Abst., 67:33998t, 1967..
|
Primary Examiner: Morris; Theodore
Attorney, Agent or Firm: Fried; Stewart J. Schwab; Jeffrey
A. Reinisch; Morris N.
Claims
What is claimed is:
1. A solution of cellulose in hydrazine where in the solvent medium
comprises at least 30% by weight hydrazine.
2. The solution of claim 1, in which the solvent medium comprises
at least 50% hydrazine.
3. The solution of claim 1, in which the solvent medium comprises
at least 70% hydrazine.
4. The solution of claim 1 containing a diluent.
5. The solution of claim 4, wherein the diluent is water.
6. A process for the preparation of a cellulose product, which
comprises dissolving cellulose in a solvent medium having at least
30% by weight hydrazine, and preparing the cellulose product from
the resulting solution.
7. The process of claim 6, wherein the solvent medium in which the
cellulose is dissolved comprises at least 50% by weight
hydrazine.
8. The process of claim 6 wherein the solvent medium in which the
cellulose is dissolved comprises at least 70% by weight
hydrazine.
9. The process of claim 6, wherein the cellulose is dissolved at
temperatures of from 100.degree. to 250.degree. C.
10. The process of claim 6, in which the cellulose dissolved has a
degree of polymerization of from 50 to 2,500.
11. The process of claim 6, wherein the hydrazine solvent is
admixed with a diluent.
12. The process of claim 11, wherein the diluent is water.
13. The process of claim 6, in which the solution is spun into a
cellulose fiber.
14. The process of claim 6, in which the solution is extruded into
a cellulose film.
15. The process of claim 6, in which the solution is formed into a
cellulose foam.
16. A process for the separation of cellulose from admixture with
lignocellulosic materials, which comprises dispersing the mixture
in a solvent medium having at least 30% by weight hydrazine and
separating the cellulose therefrom.
17. The process of claim 16, wherein the solvent medium in which
the mixture is dispersed comprises at least 50% by weight
hydrazine.
18. The process of claim 16, wherein the solvent medium in which
the cellulose is dispersed comprises at least 70% by weight
hydrazine.
Description
BACKGROUND OF THE INVENTION
This invention relates to cellulose solutions, and to the
preparation of cellulose fibers, films, foams and fabricated
articles therefrom, and to the direct extraction of cellulose from
lignocellulosic materials.
The dissolution of cellulose has been a primary objective of
workers in the art since the very dawn of cellulose chemistry.
Cellulose solutions form the basis for the commercial manufacture
of cellulose fibers, films, foams, and other cellulose molded,
shaped or otherwise manufactured articles or products (referred to
herein as "fabricated articles").
Because of its great crystallinity, relatively rigid backbone and
high melting point (decomposition temperature) cellulose is more
difficult to dissolve than related polysaccharides, e.g., starch
and dextran. The known solvents for cellulose effect dissolution by
first forming a cellulose salt or complex, e.g., a cellulose
nitrate, acetate, xanthate, ether or metallo complex. Cellulose
solvents include various concentrated mineral acids, some salt
solutions at high concentrations and elevated temperatures, various
organic amines and ammonium and diamine complexes of heavy metals
such as iron, cobalt, nickel, copper, cadmium or zinc, e.g., cuoxam
[tetramminocopper dihydroxide [Cu(NH.sub.3).sub.4 ](OH.sub.2)], or
cuene [bis(ethylenediamine) copper dihydroxide [NH.sub.2 CH.sub.2
CH.sub.2 NH.sub.2 ].sub.2 Cu(OH).sub.2 ], dibenzyldimethylammonium
hydroxide, nitrogen tetroxide in acetonitrile or dimethylformamide,
or the like. [See Encyclopedia of Polymer Science & Technology,
Kirk-Othmer, 3 (1965), page 166; Encyclopedia of Chemical
Technology, Kirk-Othmer, 2nd Ed., 4, (1965), page 601; Polymer
Handbook, Brandrup & Immergut, Chapter VI, "Properties of
Celluluse Materials", pages 14-16.]; and U.S. Pat. Nos. 1,943,176
and 3,305,499.
The use of conventional techniques such as the viscose and acetate
processes for the manufacture of cellulose and cellulose derivative
fibers and other products currently faces critical problems due to
ever-increasing capital investment, energy and pollution control
costs.
The use of various solvent-based processes for dissolving cellulose
and manufacturing fibers, films, foams or other fabricated articles
therefrom is subject to the further disadvantage that solution is
effected in these procedures by reaction to form a more soluble
cellulose salt or complex-- materials thus dissolved are mixed
products from which pure cellulose must be recovered by expensive
purification and recovery operations, or which solutions exhibit
decreased thermal stability or increased corrosive characteristics,
thus frequently precluding their use for the preparation of
cellulose fibers or foams or in similar applications.
For example, U.S. Pat. No. 3,424,702 discloses dissolving cellulose
in mixtures of liquid sulfur dioxide with aliphatic secondary or
tertiary, or alicyclic, amines. It is believed that these mixtures
effect dissolution by forming sulfite half esters with the --OH
groups of the cellulose, the amine then forming a salt or strongly
hydrogen bonding with the sulfite. Esterification breaks up the
crystallinity of the cellulose molecule and permits
dissolution.
The compound thus formed is, however, unstable, breaking down (with
degradation) slowly at room temperatures and more rapidly at
elevated temperatures. Because of this thermal instability
cellulose fibers cannot be readily prepared from such
solutions.
Accordingly, it is among the objects of the present invention to
provide cellulose solutions which may be used in the manufacture of
cellulose fibers, films, foams and other fabricated articles
without the magnified capital investment, energy and pollution
control problems to which existing processes are increasingly
subject. A further object of the invention is to provide cellulose
solutions without the use of reactive solvents, which solutions may
be directly utilized employing known techniques in the production
of cellulose products. Other objects and advantages of the
invention will become apparent from the following description of
preferred embodiments thereof.
SUMMARY OF THE INVENTION
In accordance with the present invention it has been found that
cellulose can be dissolved in hydrazine without chemical reaction
therewith, the resulting solutions being stable or metastable even
under standard temperature and pressure conditions, and thereby
permitting subsequent processing and direct conversion by
conventional techniques to form cellulose fibers, films, foams or
other fabricated articles. The cellulose solutions hereof may thus
be directly transformed by wet- or dry-spinning into fibers, or be
cast into films, without the separation and removal of reaction
impurities.
In accordance with a further feature of the present invention, it
has been found that the differential solubility of cellulose in
hydrazine vis-a-vis other wall constituents such as lignin,
hemicelluloses and pectin (referred to herein as "lignocellulosic
materials") may be utilized for the separation of cellulose
therefrom. It is thus possible to separate cellulose from raw wood,
unbleached fibers or other lignocellulosic materials without the
use of conventional kraft, sulfite or other pulping operations.
Hydrazine is not known to be a solvent for cellulose. It is known
that hydrazine effects swelling of cellulose [see, for example,
Chem. Abstracts, 48, 7893 i (1954) and Chem. Abstracts, 58, 8626 d
(1964)] or, under certain conditions, forms additional compounds
therewith [see, for example, Chem. Abstracts, 32, 1089 10 (1938);
Chem. Abstracts, 33, 4020 l (1939); Chem. Abstracts, 34, 2587 2
(1940); and Chem. Abstracts, 43, 8131 i (1949)]. It was not,
however, known prior hereto that, cellulose may be dissolved in
hydrazine, permitting subsequent processing to form cellulose
fibers, films, foams or fabricated articles therefrom.
It has now been found that at elevated temperatures cellulose
dissolves in pure hydrazine or even in hydrazine diluted with a
miscible diluent or co-solvent. Cellulose-in-hydrazine solutions
are thus formed at temperatures as low as about 100.degree. C. or
as high as about 250.degree. C. When temperatures in excess of the
boiling point of hydrazine (113.degree. C. are utilized, the system
is pressurized to maintain the constituents in the liquid phase.
Preferably, dissolution is effected at temperatures of from about
150.degree. to 210.degree. C., most desirably between 160.degree.
and 200.degree. C., use of the higher temperatures improving
dissolution. Care must, however, be taken to avoid excessive
temperatures at which charring of the cellulose may occur.
Commercially available anhydrous hydrazine normally contains water
as a diluent in an amount of at least about 3%, and frequently 4%,
by weight thereof. Cellulose is soluble in hydrazine of that
purity, and in fact in hydrazine containing up to about 30 weight %
water, under the elevated temperature conditions of this invention.
Hydrazine can also be mixed with other diluents, the latter
generally in minor proportions, and still dissolve cellulose upon
heating the mixture. The degree to which the hydrazine can be
diluted without precluding the solubility of cellulose therein
varies, depending upon the composition of the diluent, the
temperature of dissolution, the degree of polymerization (D.P.) of
the cellulose to be dissolved, the cellulose concentration, and
other parameters of the system. Generally, it is preferred that at
least 50% by weight, and preferably 70%, of the solvent medium
comprises hydrazine. Those materials which swell cellulose
themselves, e.g., dimethyl sulfoxide, can be admixed with the
hydrazine in even greater proportions (e.g., up to about 70% by
weight of the mixture thereof).
Cellulose of any desired degree of polymerization can be dissolved
in hydrazine with heating in accordance herewith. Thus, celluloses
having D.P. values as low as about 50 or as high as about 2500 so
dissolve, the dissolution of celluloses of from about 100 to 2500
being preferred, and from about 200 to 2100 particularly desired,
for fiber-forming or like purposes.
Under the indicated conditions celluloses within the range of
degree of polymerization specified can be dissolved in hydrazine in
concentrations ranging up to about 30% or more by weight. Solutions
of cellulose in concentrations in excess of about 5%, and
preferably from about 10-20%, are particularly useful for film and
fiber applications, whereas solutions having cellulose
concentrations as low as about 1% are useful for other
purposes.
The solutions thus formed can be either thermodynamically stable
true solutions of cellulose, or metastable solutions, depending
upon the above parameters, viz., the temperature, hydrazine purity
(degree of dilution), the D.P. value of the cellulose dissolved and
its concentration in the particular solution. Either form of
solution may be used in conventional processing to produce
cellulose fibers, films, foams or fabricated articles
therefrom.
While not intending to be bound by any theory, it is believed that
hydrazine dissolves cellulose under those conditions at which its
cohesive energy density approximates the cohesive energy density of
cellulose. In this regard hydrazine appears to be unique in that a
number of other solvents, e.g., 1,1-dimethylhydrazine,
dimethylsulfoxide/water, water and water/methanol mixtures (see
Control Experiments C and J-N below, respectively) have been found
ineffective to dissolve cellulose under conditions at which their
cohesive energy densities have been calculated to similarly
approximate that of cellulose. Whatever the physical mechanism by
which the solutions may be formed, however, it is intended that the
cellulose solutions and products prepared therefrom in accordance
with the present invention are limited only as defined in the
claims annexed hereto.
The cellulose in hydrazine solutions hereof may be dry-spun into
fibers by extruding a stream of such a solution through an
extrusion zone and into contact with a heated evaporative medium to
evaporate the solvent therefrom. Alternatively, the solutions may
be subjected to conventional wet-spinning wherein a viscous dope
thereof is injected into a non-solvent, coagulated and stretched
into fibers. In certain cases, the solutions hereof may also be
subjected to flash-spinning by extrusion under elevated temperature
and pressure through an apertured spinnerette into air at normal
pressure as described, for example, in U.S. Pat. No. 3,542,715.
Cellulose fibers may thus be formed from the solutions hereof
employing known fiber-forming techniques.
Cellulose films may be prepared from the solutions hereof by
casting dopes thereof and evaporating the solvent or extruding into
a coagulating bath, either with or without subsequent uniaxial or
biaxial orientation of the film.
Cellulose foams may be produced from the concentrated solutions by
casting blocks and leaching out the solvent with water, for
example; or by incorporating therein hydrazine-insoluble materials,
casting blocks therefrom, coagulating the same or allowing it to
crystallize, and leaching out the insoluble materials.
Alternatively, foams may be produced by flashing at least a portion
of the hydrazine solvent to effect boiling and consequent foaming
thereof. Blowing agents, low boiling co-solvents, or other
conventional additives may be added to the solution as recognized
in the art.
Further, other fabricated cellulose articles may be prepared from
the solutions of the invention by casting, molding or extruding the
desired fabricated articles therefrom. In this manner, structural
members of any predetermined configurations may be directly
produced from the cellulose-in-hydrazine solutions.
The dissolution of cellulose in hydrazine may, as indicated
hereinabove, also be utilized for the separation of cellulose from
admixture with lignocellulosic materials or for direct utilization
of the whole materials without separation. Separation may be
effected, for example, by dispersing wood chips, shavings or the
like in hydrazine, and utilizing the differential solubility of the
cellulose and the lignocellulosic materials in the hydrazine to
separate the same. The cellulose may thereafter be subjected to any
desired technique for production of fibers or films or other
desired end products.
PREFERRED EMBODIMENTS OF THE INVENTION
Preferred embodiments for preparing cellulose solutions, for
producing cellulose fibers, films and foams therefrom, and for
extracting cellulose from lignocellulosic materials with hydrazine,
are illustrated hereinafter. In the following discussion and the
several illustrative examples all parts and percentages are given
by weight, unless otherwise specified. All temperatures are given
in degrees Celsius and all pressures in pounds per square inch
gauge.
As indicated hereinabove, the conditions utilized to effect
solution of the cellulose can vary, depending upon a number of
interrelated parameters, including the degree of polymerization of
the cellulose to be dissolved, the concentration of the cellulose
in the hydrazine solvent, the amount of water or other diluent
present or admixed with the solvent, and the temperature at which
dissolution is effected. For example, utilizing a cellulose with a
D.P. of about 550 and a substantially anhydrous hydrazine solvent,
cellulose may be dissolved in concentrations of 30%, at
temperatures of about 200.degree. C. As another example, utilizing
celluloses of 2100 D.P., solutions of about 10% concentration can
be prepared under substantially the same conditions. The specific
conditions required to dissolve specific amounts of cellulose in
the hydrazine solvent can vary widely, dependent upon the
parameters of the particular system employed.
In experiments conducted in accordance herewith "anhydrous"
hydrazine containing 4% water dissolved a D.P. 2100 cellulose. On
the other hand, hydrazine hydrate (containing about 35% by weight
water) did not dissolve the relatively high molecular weight
cellulose (see Control A below). Lower molecular weight celluloses
may, however, be dissolved in hydrazine containing proportions of
water up to about 30% by weight of the hydrazine/water
solution.
As noted herein, other diluents, stabilizing agents or other
additives can be incorporated in the hydrazine solvent system,
without precluding solution. The addition of such additives can be
useful in commercial operations to minimize costs and the risks
attendant use of the volatile and potentially explosive hydrazine
solvent.
Examples of suitable stabilizing agents for hydrazine are sulfamido
acetate salts such as described in U.S. Pat. No. 2,680,066; and
aluminum, zinc and cadmium oxides as disclosed in U.S. Pat. No.
2,837,410. Other known stabilizing agents can also be utilized in
the solutions formed in accordance with this invention.
Examples of suitable diluents which can be incorporated in the
cellulose solutions hereof comprise inert polar solvents such as
N-methyl pyrrolidone, dimethyl acetamide, ammonia, methylamine,
ethylamine, ethylene diamine, dimethyl hydrazine, methanol,
dimethyl sulfoxide, and glycols, ethanolamines and the like in
proportions such that sufficient hydrazine is present to effect
dissolution of the cellulose.
Other additives known to enhance the solubility of cellulose and to
be stable in the hydrazine solutions hereof can be incorporated in
the cellulose solutions. Thus, quaternary ammonium hydroxides,
e.g., the dibenzyldimethylammonium hydroxide referred to
hereinabove, or similar basic solvents may be so utilized in the
solvent system.
The presence of low boiling diluents is particularly desirable in
the preparation of solutions from which it is desired to prepare
cellulose fibers and foams by flashing. The addition of a diluent
having a latent heat of vaporization substantially lower than that
of hydrazine is necessary to permit flashing of all, or
substantially all, of the hydrazine at elevated temperatures. For
example, it has been found that cellulose foams can be produced by
flashing hydrazine/ethylene diamine or hydrazine/ammonia cellulose
solutions. Foams thus formed are useful in a variety of
applications. For example, they can be used as packing materials or
absorbents.
The following examples further illustrate preferred embodiments of
the processes, compositions and products of the present invention.
In these examples, as well as in the preceding description, unless
otherwise indicated all parts and percentages are given by weight
and all temperatures are in degrees Celsius.
EXAMPLES 1-4
Dissolution of Cellulose in Hydrazine
In the following examples cellulose was dissolved in hydrazine
under elevated temperature and pressure conditions within high
pressure Fischer and Porter aerosol tubes (Carius combustion
tubes). The aerosol reaction tubes were immersed in a stainless
steel beaker of approximately nine quart capacity filled with
peanut oil to serve as a heating bath. Each reaction tube was
connected at the top through suitable high precision Cajon adapters
to a pressure gauge, a needle valve and a safety relief valve.
(Temperatures within the reactor tubes were determined based on the
pressures developed.) The reaction tube-valving system was raised
or lowered into the oil-bath at will with the aid of a remote
controlled reversible synchronous motor. A Fischer-Scientific
Safety Shield was placed in front of the apparatus. The oil bath
was maintained at .+-.1.degree. C. of the predetermined temperature
settings by connecting an electronic relay to a mercury contact
thermoregulator (0.degree.-300.degree. C.) and the immersion
heater.
In each of the following examples cotton linter flock (97-98% alpha
cellulose, DP=2100) was the cellulose employed.
TABLE I
__________________________________________________________________________
DISSOLUTION OF COTTON LINTER FLOCK IN HYDRAZINE
__________________________________________________________________________
Ultimate Concentration Pressure of Cellulose Bath Developed, Exam-
in Hydrazine Temperature Time & ple (wt.%) (.degree. C.)
Temperature (.degree. C.) Comments
__________________________________________________________________________
1 1 225.degree. 40 psi After 5 minutes heating cellulose dispersed
com- (about 170.degree.) pletely and after 15 minutes heating
(40-50 psi) complete dissolution occurred, giving a transparent
solution. 2 2 225.degree. 80 psi Complete dispersion at 10 psi and
complete solution (about 180.degree.) at 80 psi; no precipitation
upon cooling to room temperatures and atmospheric pressure. After
20 hours standing the solution, which had been a transparent gel,
became cloudy and turned solid in another 3-4 days. 3* 10
250.degree. 100 psi Under these conditions the cellulose completely
dissolved. 4 4 250.degree. 100 psi Under these conditions the
cellulose completely (about 190.degree.) dissolved. The solution
was poured, with agi- tation, into water. Globules of liquid thus
formed turned opaque gradually (after about one-half hour).
__________________________________________________________________________
*In this example a 70/30% (v/v hydrazine/ethylene diamine mixture
was utilized as the solvent for the cellulose.
The species dissolved in Example 4 was characterized as cellulose
as follows. First, the opaque globules of the precipitated
cellulose were washed repeatedly with water and dried under vacuo
for 22 hours at 40.degree. C. to remove the hydrazine.
Fourier-Transform infrared spectra were obtained for the raw and
treated cellulose using KBr pellets. The crystallinity indices
calculated by the method of Nelson, O'Connor [J. Applied Poly.
Sci., 8, 1325 (1964)] were 0.95 for the raw sample and 1.0 for the
treated material. X-ray diffractograms on pressed pellets gave a
crystallinity of 89% for the raw material and 75% for the treated
sample. These were determined by the method of Segal et al [J.
Applied Poly. Sci., 8, 1325 (1964)]. The raw material had an X-ray
pattern corresponding to the structure of cellulose I while that of
the treated sample corresponded to the structure of cellulose
II.
CONTROL EXPERIMENTS A-N
Attempted Dissolution of Cellulose in Other Solvents
In the following further experiments it was attempted to dissolve
samples of the same cotton linter flock used in Examples 1-4 in a
variety of other solvents, employing the same experimental system
and conditions as utilized hereinabove; the results thus obtained
are recorded in Table II:
TABLE II
__________________________________________________________________________
ATTEMPTED DISSOLUTION OF COTTON LINTER FLOCK IN MISCELLANEOUS
SOLVENTS
__________________________________________________________________________
Ultimate Solvent and Pressure Concentration Bath Tem- Developed,
Con- of Sample There- perature Time & trol in (wt. %) (.degree.
C.) Temperature (.degree. C.) Comments
__________________________________________________________________________
A hydrazine 225.degree. 120 psi; 2 hrs. Highly swollen; no
discoloration; no sharp increase hydrate, (about 180.degree.) in
swelling at any stage. 1% B 50/50 (v/v) 250.degree. 100 psi No
dissolution of cellulose; considerable swelling hydrazine/ (about
220.degree.) observed. ethylene di- amine, 10% C 1,1-dimethyl
250.degree. 180 psi; 1 hr. Considerable swelling of cellulose but
no dispersion or hydrazine, 1% solution observed. D ethylene
diamine 225.degree. 70 psi; 1 hr. Swelled 5-6 fold but no
dispersion occurred. 1% E ethylene dia- 225.degree. 120 psi; 1 hr.
Swelled about 4 fold; no dispersion. mine/H.sub.2 O, 1% F
formamide, 1% 250.degree. 15 psi; 1/2 hr. No swelling. G
morpholine, 1% 250.degree. 90 psi; 1/2 hr. No swelling. H ethylene
250.degree. 15 psi; 1/2 hr. No swelling. glycol, 1% I 6% SO.sub.2
in water 225.degree. 150 psi; 1 hr. No swelling or dispersion*
(H.sub.2 SO.sub.3 solu- (about 180.degree.) tion), 1% J 70/30 DMSO/
220.degree. 60 psi; 2 hours No swelling or solubility water, 1% K
water, 1% 280.degree. 220 psi; 2 hrs. No swelling or solubility;
pulp turned grey. Upon cooling (about 200.degree.) the supernatant
liquid, no trace of precipitation was observed; the cellulose pulp
retained its strength when manually tested. L 90/10 water/
220.degree. 100 psi; 2 hrs. No swelling or solubility methanol, 1%
(about 170.degree.) M 80/20 water/ 220.degree. 110 psi; 2 hrs. No
swelling or solubility. methanol, 1% N 70/30 water/ 220.degree. 120
psi; 2 hrs. No swelling or solubility. methanol, 1%
__________________________________________________________________________
*Cf., Junio Hata and Kingo Yokota Sen-1 Gakkaishi, 24(9), pp.
415-424 (1968); U.S. Patent No. 3,424,702.
EXAMPLES 5-9
Dissolution of Cellulose in Hydrazine at Varying Concentrations and
Preparation of Films and Fibers Therefrom
In the following examples various weights of cellulose were
dissolved in hydrazine, utilizing the aerosol reaction tubes as
described above in connection with Examples 1-4 to provide
solutions with various concentrations of cellulose. To assist in
stirring the high viscosity mixtures a large Teflon-coated magnetic
stirrer was immersed in each reaction tube, a hand-held magnet
being moved outside of the tube to motivate the magnet.
EXAMPLE 5
Dissolution of Cotton Linter Flock, 1% in Hydrazine Solution
In this example 0.25 g of the same cotton linter flock utilized in
the previous examples were cut into small pieces and immersed in 25
ml anhydrous hydrazine within the reaction tube. The tube was
placed in the oil bath at about room temperature, and the bath was
then heated.
The hydrazine initially swelled the cellulose about 4-5 times its
original volume. After five minutes at 55.degree. C., the cellulose
began to disintegrate. By 139.degree. C. the cellulose had
completely disintegrated. At 186.degree. C. (20 psi) the mixture
began to thicken. At 195.degree. C. (29 psi) the mixture began to
clear. At 200.degree. C. (34 psi) the mixture was quite viscous and
almost clear. At 203.degree. C., the mixture was completely clear
and quite viscous.
The tube was cooled to room temperature by removing it from the
bath, and allowing it to cool in air. When the pressure dropped to
atmospheric, the solution remained clear. The solution in the
unopened tube was still clear the next day.
EXAMPLE 6
Dissolution of Cotton Linter Flock, 5% in Hydrazine Solution, and
Preparation of Films and Fibers Therefrom
In this example 3.5 g of the aforesaid cotton linter pulp and 70 ml
hydrazine were charged to the reaction tube. A larger magnetic
stirrer was placed in the tube than utilized in Example 5 in order
to obtain greater agitation of the higher viscosity solution
produced.
The tube was immersed in the oil bath at 180.degree. C. and removed
frequently for stirring. At 20 psi the solution started to thicken.
With good stirring, at 190.degree. C. all of the cellulose, except
for a small amount on the bottom, had dissolved. The tube was then
heated for 20 minutes at 195.degree. C. The small amount of
insoluble material remained adhered to the bottom and sides of the
reaction tube.
After cooling, the solution was free from bubbles. At 50.degree. C.
it was poured onto clean glass plates, and spread with a Gardner
knife to form wet films having thicknesses of 20, 35 and 60 mils.
The hydrazine can be removed by evaporation to provide cellulose
films useful for wrappings.
A portion of the solution was wet-spun into fiber by pouring the
same into a plastic disposable syringe and injecting it into a 10%
acetic acid solution through a No. 19 needle. The extrudate was 1.5
mm in diameter. The needle was removed, and the solution extruded
through the opening, giving a 3 to 4 mm thick extrudate. When this
was stretched slowly, it necked down to a fiber and whitened. When
this was pulled slowly (1 cm/sec), a continuous fiber was spun from
the tip of the extrudate. Several lengths of fiber were left in the
acetic acid solution overnight, and then air-dried.
Flat plate X-ray photographs were taken of the cellulose fibers and
films produced as described in Example 6. The fiber showed slight
orientation and five reflections could be seen. The air-dried film
showed five reflections and appeared to be highly crystalline since
there was little amorphous scattering. The Bragg spacings for the
fiber and film are listed in Table III.
TABLE III ______________________________________ Bragg Spacings of
Cellulose Fiber and Film of Example 6
______________________________________ Fiber Film Cellulose II*
Cellulose II** ______________________________________ d(A) d(A)
d(A) d(A) 7.27 7.35 7.26 7.18 4.45 4.33 4.48 4.44 4.35 4.14 4.10
4.05 3.16 3.08 3.13 2.48 2.53 2.55 2.18 2.21, 2.23, 2.12
______________________________________ *J. Appl. Polymer Sci., 8,
1325 (1964). **Strongest reflections of annealed fibers of rayon
(Cellulose II). Private communication, Dr. J. Blackwell, Case
Western Reserve University, to be published.
The infrared absorption spectrum of a 1/2 mil cast film prepared as
described in Example 6 was determined. The crystallinity index
ratio proposed by Nelson and O'Connor [J. Appl. Polymer Sci., 8,
1325 (1964)], the ratio of absorption at 1372 cm.sup..sup.-1 to
absorption at 2900 cm.sup..sup.-1, was used to estimate the
crystallinity of the cast film. The ratio was 0.75. A known
cellulose possessing maximum crystallinity may be obtained, for
example, by hydrolyzing Fortisan, a highly crystalline Cellulose
II, to remove the amorphous regions thereof and produce Fortisan
hydrocellulose. Such a hydrocellulose has a ratio of 0.75 to 0.76;
this corresponds to an 85% crystallinity by X-ray techniques. The
highest crystallinity index ratio found for unhydrolyzed Cellulose
II is 0.68 for a Fortisan rayon, which corresponds to 80% X-ray
crystallinity.
EXAMPLE 7
Dissolution of Cotton Linter Flock, 7% in Hydrazine Solution and
Preparation of Films and Fibers Therefrom
5.0 g of a cotton linter flock material (CL-100, obtained from
International Filler, a material constituted of 97% alpha cellulose
and having a DP equal to 2,100) was charged with 70 ml hydrazine to
a reaction tube. The tube was immersed in the oil bath at
150.degree. C. The solution thickened as the temperature rose.
Stirring was done frequently with the hand-held magnet. At
195.degree. C. the mixture started clearing (70 psi). After several
minutes heating at 200.degree. C. the mixture cleared
completely.
Films and fibers can be formed from the cellulose solution thus
produced.
EXAMPLE 8
Dissolution of Cotton Linter Flock, 7% in Hydrazine Solution and
Preparation of Films and Fibers Therefrom
5.0 g of the cotton linter flock was mixed with 70 ml hydrazine in
the reaction tube. The oil bath was preheated to 180.degree. C. and
the tube immersed therein. Violent refluxing occurred. The tube was
periodically immersed and then removed from the bath until the
pressure reached 10 psi. At 20 psi the reaction tube was removed
and the solution mixed with the magnetic stirrer. The bottom of the
cellulose mixture was quite viscous and could not be manually
mixed.
The heating and mixing procedure was repeated until the tube
reached a pressure of 50 psi, at which point the magnetic stirrer
was no longer operable. Heating was thereafter continued to
195.degree. C. After cooling, an attempt was made to manually break
up the mass of cellulose at the bottom of the reaction tube with a
metal rod. It was so tough and rubbery that this was not
feasible.
Films and fibers were produced by re-heating the cellulose mass,
and thereafter casting and extruding the same from the resulting
solution.
EXAMPLE 9
Dissolution of Cotton Linter Flock, 10% in Hydrazine Solution and
Preparation of Films and Fibers Therefrom
7 g of the cotton linter flock and 70 ml hydrazine were charged to
a reaction tube. The tube was heated with stirring. Gel formation
occurred on the sides of the tube. The tube was repeatedly immersed
in the oil bath, removed, and the tube sides scraped with the
magnetic stirrer. After two hours of repeated immersion and
stirring, gel formation precluded complete solution formation.
By the time bubbling of the solution terminated, it was too viscous
to permit escape of the bubbles formed. Voids were therefore formed
in the films cast from the partial solution. Fibers were also drawn
from the cellulose mixture.
It may be seen from Examples 5-9 that the viscosity of the solution
is dependent on the concentration of the cellulose solution.
Employing efficient stirrers and lower D.P. celluloses, solutions
having cellulose concentrations greater than 10% can be
prepared.
Most of the cellulose in hydrazine solutions produced in Examples
6-9 remained clear at room temperature for as long as four or five
days. Some samples began to cloud after only one day. It is
apparent that the cellulose remained in solution for a sufficient
period to permit subsequent processing for the formation of films,
fibers, foams or fabricated articles therefrom.
EXAMPLE 10
Preparation of Cellulose Foam from Solutions of Cotton Linter Flock
in Hydrazine/Ethylene Diamine
A cellulose foam can be prepared in the following manner: A
cellulose solution in a 70/30% (v/v) hydrazine/ethylene diamine
mixture was formed as in Example 3. Upon release of the pressure in
the reaction tube from 100 psi to atmospheric pressure some of the
solvent flashed off, leaving a viscous, foamy product at the base
of the collection flask. The product solidified after 20 hours and
was washed with water. Examination under microscope revealed a
foamed structure.
EXAMPLE 11
Dissolution of Low Molecular Weight Dissolving Pulp in
Hydrazine
A low molecular weight cellulose dissolving pulp (Rayonier Corp.,
R550) having a D.P. of 550 was dissolved in anhydrous hydrazine
(96-97% purity) employing the procedure and equipment described in
Example 1. At 0.1% concentration cellulose, a solution formed at
180.degree. C. after mixing for 55 minutes. At 33% concentration
the cellulose was dissolved after mixing for 450 minutes at
temperatures reaching 201.degree. C.
Useful films and fibers can be formed from these solutions in the
manner described above.
EXAMPLE 12
Dissolution of High Molecular Weight Dissolving Pulp in
Hydrazine
When in Example 11, a higher molecular weight cellulose dissolving
pulp, having a D.P. of 1650, is employed (Rayonier Corp., R 1650),
the same or similar results are obtained in that the cellulose
material dissolves in hydrazine, and useful films and fibers can be
formed therefrom.
EXAMPLE 13
Separation of Cellulose from Lignocellulosic Materials
Oak shavings were dispersed in anhydrous hydrazine under ambient
conditions (about 20.degree. C.) and heated under pressure until
solution occurred (190.degree. C.). The solution was cooled, a gel
mass forming therein. Water was added to the residual solution, a
colored precipitate forming. On standing, the precipitate whitened,
the colored impurity settling out. The white precipitate was
cellulose.
EXAMPLE 14
Dissolution of Cellulose in Hydrazine/Diluent Mixtures
A 1% solution of cotton linter flock in hydrazine was prepared in
the manner described in Example 1. Appropriate amounts by volume of
various diluents were mixed with hydrazine in 20 ml vials to give
10 ml of each mixture. Approximately 0.2 ml of the 1% cellulose
solution in hydrazine was added to each mixture, the vial sealed
and stirred at room temperature. Solubility of the cellulose was
judged by the absence or appearance of a cellulose precipitate. To
test for the possibility of a gel dispersion, excess diluent was
added. The generation of a dispersed, fibrous precipitate confirmed
the original solubility. The data are summarized in the following
tabulation:
TABLE IV ______________________________________ SOLUBILITY OF
CELLULOSE IN HYDRAZINE/DILUENT MIXTURE
______________________________________ Hydrazine/Diluent Diluent
Ratio by Volume Behavior ______________________________________
Methanol 75/25 Soluble Methanol 50/50 Precipitated 1,1-Dimethyl
hydrazine 75/25 Soluble 1,1-Dimethyl hydrazine 50/50 Precipitated
Dimethyl Sulfoxide 75/25 Soluble Dimethyl Sulfoxide 50/50 Soluble
Dimethyl Sulfoxide 40/60 Soluble Dimethyl Sulfoxide 30/70
Precipitates after five minutes Dimethyl Sulfoxide 20/80 Insoluble
N-methyl pyrrolidone 70/30 Soluble N-methyl pyrrolidone 50/50
Insoluble NH.sub.3, anhydrous.sup.2 14/25 Soluble NH.sub.3,
anhydrous.sup.2 14/30 Precipitated
______________________________________ .sup.1 A 5% solution was
used which did not disperse. The edges of the viscous mass turned
white. .sup.2 Cellulose was initially dissolved in the hydrazine in
0.3% concentration. NH.sub.3 was added in a closed system, under
pressure at room temperature.
It will be understood that various changes may be made in the
parameters of the processes, compositions and products described
hereinabove without departing from the scope of the present
invention. Accordingly, it is intended that the invention is not
limited by the preceding description of preferred forms thereof,
but only by the following claims.
* * * * *